Vinyl chloride polymers stabilized with mixtures of 4, 4&#39;-methylene bis-omicron-cresol and omicron-cresol-formaldehyde polymers



' s 245 94s VINYL CHLORIDE PoLYK IERS STABILIZED WITH MIXTURES or 4,4-METHYLENE BIS-'O-CRESOL 'AND o-cREsoL-FonMALDEnYDE POLYMERS Wendell A. Barnes, Cheswick, and Norman W. Franke,

Penn Hills Township, Allegheny County, Pa., assiguors to Gulf Research & Development Company, Pittsburgh, Pa, a corporation of Delaware No Drawing. Filed June 24, 1963, Ser. No. 290,249

9 Claims. (Cl. 260-313) compositions comprise a resinous vinyl chloride polymer,

a plasticizer and one or more stabilizers. One of the .indicia of a good resinous vinyl chloride polymer formulation for electrical insulation is the percent retention of elongation after an accelerated aging at elevated temperatures. The Underwriters approval varies from 50 to 70 percent retention for various types of thermoplastic insulated wire. The resinous vinyl chloride polymer compositions of this invention have unexpectedly excellent percent retention of elongation properties after aging as well as good color properties.

In accordance with the invention, improved plastic electrical wire coating compositions comprise a resinous vinyl chloride polymer, a neutral branched-chain alkyl ester, having between 6 and 13 carbon atoms per alkyl group, of a polybasic acid, and between 0.04 and weight percent of the vinyl chloride polymer of a stabilizer consisting of a mixture of between 50 and '90 weightpercent of 4, 4'-methylene bis-ortho cresol and between 10 and 50 weight percent of a polymer of o-cresol and formaldehyde.

The compositions of this invention contain a resinous vinyl chloride polymer. The term resinous vinyl chloride polymer includes, in addition to homopolymers, a resinous copolymer of vinyl chloride and vinyl acetate wherein the weight percent vinyl chloride is at least 85 I percent, and is preferably between 85 and 97 percent.

Various esters are known in the art to be useful a plasticizers for vinyl chloride type polymers. Branched-chain neutral alkyl esters, such as those obtained by the esterificaticn of polybasic acids with branched-chain alcohols having between 6 and 13 carbon atoms per molecule, are particularly suitable for this purpose. The esters should be neutral, that is, no free acid groups should remain after esterification. The desirable polybasic acids or anhydrides are normally those having between 2 and 4 carboxyl groups and between 4 and 14 carbon atoms per molecule. Dibasic acids or anhydrides are preferred which have between 5 and 10 carbon atoms per molecule. Suitable specific examples of polybasic acids include phthalic acid; phthalic anhydride; adipic; pimelic; succinic; cumenyl succinic; sebacic; azelaic; diglycolic; isophthalic; and trimellitic. The most preferred acid is phthalic acid.

The branched-chain alcohols required for preparing the ester plasticizers of the compositions of this invention can be obtained from any suitable source. For example, 2-ethylhexyl alcohol can suitably be employed. The preferred alcohols, however, are those produced by the .hydroformylation of branched-chain olefins (the celebrated oxo process). A typical isomer distribution for isooctyl alcohol is given on page 33 of the book Higher Oxo Alcohols by L. H. Hatch, New York,

United States Patent 0 John Wiley & Sons, 1957. The oxo alcohols consist of isomers having at least one tertiary carbon atom, and usually the isomers have two tertiary carbon atoms. The tridecyl alcohol (C predominates in tetramethylnonanols. The higher OX0 alcohols apparently have no isomers with a quaternary carbon atom.

The esters can be prepared by any suitable procedure. One suitable procedure comprises contacting the selected alcohol with the selected dibasic acid in the presence of a strong mineral acid, such as sulfuric, and recovering the desired ester therefrom.

The amount of ester plasticizer in the resinous vinyl chloride polymer compositions of this invention can vary between 20 and '80 weight percent of the vinyl chloride polymer and preferably is between 30 and 60 weight percent. Secondary plasticizers well known in the art can also suitably be employed, such as t-butyl naphthalene.

Stabilizers are used to reduce the degradation of the resinous vinyl chloride polymer from various causes such as heat and light. These stabilizers are more commonly known as hydrogen chloride acceptors. Various stable metal compounds are employed as hydrogen chloride acceptors. By stable metal compounds is meant at least one compound of a metal selected from the group consisting of cadmium, barium, zinc, tin and lead which does not decompose and has essentially no volatility at 350 F. and atmospheric pressure. One suitable class of metal compounds are the basically reacting metal salts of organic acids having between 1 and 20 carbon atoms. Another suitable class of metal compounds are the basically reactingmetal sulfates. Still another class of suitable metal compounds are the basically reacting metal silicate sulfates. Lead stabilizers are used in practically all of -the commercial polyvinylchloride electrical compounds.

Suitable specific examples of known stabilizers for use in'resinous polyvinylchloride include dibasic lead phthalate, basic lead silicate sulfate, hydrous tribasic lead sulfate, dibasic lead stearate, dibasic lead carbonate, dibasic lead phosphate, dibutyl tin dilaurate and dibutyl tin diacetate. The preferred stabilizers include dibasic lead phthalate, basic lead silicate sulfate and hydrous tribasic lead sulfate.

The concentration of the .above metal compound stabilizers to employ can vary from about 1 to 12 weight percent of the resinous vinyl chloride polymer with preferred amounts between 3 and 10 weight percent.

It has been found, however, that where branched-chain ester plasticizers, such as those prepared from oxo alcohols, are employed, the addition of metal compound stabilizers is not sufficient. This is found to be particularly true when the resinous vinyl chloride polymer is destined for use in a coating composition for electrical wire insulation, since the resinous vinyl chloride polymer with the metal compound stabilizer alone does not meet the requirements for retention of elongation after aging.

Certain auxiliaryfstabilizing agents have now been found which, when added to resinous vinyl chloride polymers, unexpectedly improve the vinyl chloride polymers, especially as a coating composition for electrical wire insulation, since the retention of elongation of the resinous vinyl chloride polymer after aging is exceptionally high and the colors are exceptionally good. While it is not certain just how these auxiliary stabilizers work, it is believed the auxiliary stabilizers prevent thermal degradation of the branched-chain ester in addiformaldehyde polymer. 7 tween 50 and 90 weight percent of the 4,4-methylene the 4,4'-meth lene biso-cresol and a polymer of aldehyde-o-cresol can be obtained.

been employed in the examples .to follow consists essentially of about 70 weight percent of the 4,4'-methylene bis-o-cresol and about 30 weight percent of the o-cresol- The mixture can contain bebis-o-cresol and preferably between 60 and 80 weight percent while the amount of the o-cresol-formaldehyde polymer can 'varybetween about 10 and 50 weight per- 1 "cent with preferred amounts bet'ween 20 and 40 weight 9 percent of the mixture.

TheI'o-cresol forfnaldehy de polymer. which is used in -admixture with the 4,4-met hylene bis-o cresol is a poly- "mer having 'a' molecular weight of between about 300 and 1000, with a preferred molecular weight between :about 450 and 850.-

The amount of mixed stabilizer to employ can vary between about 0.04 and 5 weight percent of the vinyl chloride polymer with preferred amounts between 0.05

and 4 weight percent.

The 4,4-me thylene bis-o-cresol can be prepared in any manner well known in the art. For example, 4,4f-

.methylene bis-o-cresol can be prepared by-the reaction .of o-.cresol and formalin (aqueous formaldehyde) at re- .flux temperature in the presence of an acidic catalyst,

such 'as sulfuric or oxalic acid. By allowing the reaction to proceed for longer reaction times, a mixture of form- Fillers can also suitably be employed in the compositions of the subject invention if. desired. The function of a filler is sometimes solely as a low-cost extender, but a filler can be employed to impart additional desired prop- ,erties to the resinous polyvinylchloride. A finely divided clay" is used as the principal filler in the vinyl electrical compositions of the .subjectinvention. Other suitable fillers include calcium carbonate, silica and alumina. The amount of filler can vary between and 50 weight percent of the polyvinylchloride' with preferred amounts between 5 and 20 weight percent.

.A lubricant, such as stearic acid, can also be em- .ployed to -aid in processing the compositions of this invention. The amount of lubricant can vary between 0.1

.and 1.0 weight percent of the polyvinyl chloride "with' preferred amounts between 0.2 and 0.5 weight percent. Insulated electric wire is classified as to the maximum temperature to which it is subjected in use. Under- .writers Laboratories set the standards for most of the ;building and appliance Wire used in the United States. .Since the phthalate esters and the resinous vinyl chloride type electrical wire compounds plasticized with them are regarded as having satisfactory electrical properties, the .critical test that they must pass to be used in electrical insulation is the retention of elongation after oven aging.

Underwriters Laboratories has an accelerated aging test .in a mechanical convection oven for wire compounds. In this test'the wire compound is subjected to a temperature above that of its maximum operating temperature in use, as designated by its class for seven days. To pass this test the wire compound must have a minimum retention of elongation as shown in Table I below. The percent retention of the property is calculated by dividing the -value measured on a specimen after oven aging by the value obtained on an unaged specimen taken from the same sheet. I

TABLE I Oven Time in Percent Class temp., Oven, retention, C. days elongation 80 C.Appliancc wire a 118 7. i 65 90 C.Appliance wire 121 7 65 105 C..Applianee wire a 136 7 65 Underwriters Laboratories, Inc. Subject 758, issued October 5, 1950, revised March 21, 1961, entitled Outline of Proposed Inyestigation Thermo lastic-Insulated App a c -Up W red.

than :tlO percent.

.than on the composition of the sample.

oven, and V 'flow of 400 ft./min. and with the freshair inlet oneaging.

The C., C. and C. appliance wires, formerly called radio hook-up. wire, are for the indicated maximum temperature and'are used, as the name indicates, in electrical appliances.

In oven aging runs madeinan unmodified oven the variations in elongation retention were found to be greater In this type of oven the results depended more on the position of the specimen in the oven Since Underwriters Laboratories; use an unmodified oven in this test, insulated wire manufacturers put a safety factor in'their wireformulations. While the unmodified ojven simulates commercial practice it is too erratic to determine small differences in auxiliary stabilizers. To overcome this ditficulty, an Apex-Royen tubular oven unit was installed in a Blue M. Model POM- RAZ oven. The tubular 'oven has dampers to control the air flow over the specimens in each tube. The air flow over the specimens seems to be as important as the temperatures.

In the examples which follow, the vinyl chloride polymer compositions were subjected to the 105 C. wire test. In the 105 C. wire tests two dumbbell shaped specimens were placed in each of the sixteen tubes of the were aged 7 days at 136, C. with an air fourth open. p v

To calibrate the oven, the 105 C. test was run on Geon 8630, a commercial 105 C. wire compound made by 30 B. F. Goodrich Chemical Company.

Geon 8630 was found in this work to have an average elongation retention of 80 percent in the 105 C. test, which is within the range claimed for this material. 7

Test specimens had the following compositions;

'100-parts of resinous vinyl chloride polymer;

50' parts of ditridecylphthalate plasticizer; 15 parts of filler; 7 parts of a metal compound stabilizer;

;0.5 part of a lubricant; and between 0 and 1 part of an auxiliary stabilizer.

The resinous vinyl'chloride polymer (Geon 101) was a copolymer of vinyl chloride and vinyl acetate in a 95:5 ratio of monomers. The ditridecylphthalate plasticizers had a molecular weightof 530, a specific gravity of 0.950,

chased from the Southern Clay Company.

The metal compound stabilizer was dibasic lead phthalate.

The lubricant was stearic acid.

The exact amount and type of auxiliary stabilizer is given in each of the examples below.

The ingredients were mixed for 10 minutes and the premixed composition was placed on hot rolls of a 6" x 13" laboratory mill, and milled for 7 minutes at 340345 F. during which time the sheet was cut back and forth to thoroughly blend the stock. A 6" x 6" panel of the 50 mil sheet from the mill was prepared for testing by molding in a hydraulic press at 330 F. under 1000 pounds pressure for five minutes and 10,000 pounds pressure for anadditional five minutes. 1

All of the samples were aged at constant temperature and humidity (7 3 :2? F., 50- -2 percent relative humidity) for a minimum of 24 hours before and after oven Example 1 In this example, 0.1. phr. of a mixture of 70 weight percent 4,4'-methylene bis-o-cresol and 30 weight, percent of apolymerof formaldehyde and o-cresol having a weight average molecular weight of about 700 was employed as .the. auxiliary stabilizer. .The term phr. means parts per hundred parts of resin. The percent retention of elongation was 77 and the color was excellent being light gray.

Example 2 Example 1 was repeated except the amount of auxiliary stabilizer was reduced to 0.05 phr. The percent retention of elongation was 71 and the color was still excellent, being a medium gray.

Example 3 Example 4 In this example, 0.1 phr. of 4,4'-methylene bis-o-cresol was employed as the auxiliary stabilizer. The percent retention of elongation was 76 while the color was much poorer, being medium yellow.

Example 5 Example 4 was repeated except the amount of 4,4'- methylene bis-o-cresol was reduced to 0.03 phr. The percent retention of elongation was only 28 and the color of the final composition was still yellow.

A comparison of Examples 4 and 5 with Examples 1 and 3 shows that for similar concentrations the use of the auxiliary stabilizer of this invention results in vinyl chloride polymer compositions of improved color over the use of 4,4'-methylene bis-o-cresol alone. Thus, the use of 4,4'-methylene bis-o-cresol in admixture with a polymer of o-cresol and formaldehyde unexpectedly results in an improvement in the color of the resulting vinyl chloride polymer compositions.

A comparison of Example 5 with Example 2 shows also the unexpected beneficial effect of the added o-cresolformaldehyde polymer. Thus, in Example 5, 0.03 phr. of 4,4'-methylene bis-o-cresol resulted in an unacceptable vinyl chloride polymer composition both from a color (yellow) and a percent retention of elongation (only 28) standpoint. In Example 2, the amount of 4,4'-methylene bis-o-cresol was 70 percent of 0.05 or 0.035 phr. The percent retention of elongation was an acceptable 71 while the color was excellent. Thus, while the amount of 4,4-methylene bis-o-cresol was only slightly more in Example 2 than in Example 5, the percent retention of elongation and color of the resulting vinyl chloride polymer composition were unexpectedly greatly improved. This improvement, although not understood, is attributed to the presence of the o-cresol-formaldehyde polymer.

Example 6 In this example, no auxiliary stabilizer Was employed. The percent retention of elongation was only about 12.

A comparison of Example 6 with Example 1 shows the unexpected beneficial eifect of the auxiliary stabilizers of this invention.

Resort may be had to such variations and modifications as fall within the spirit of the invention and the scope of the appended claims.

We claim:

1. A composition of matter comprising a major por tion of a resinous vinyl chloride polymer selected from the group consisting of vinyl chloride homopolymers and vinyl chloride-vinyl acetate copolymers wherein at least 85 weight percent of the copolymer is vinyl chloride, a neutral branched-chain alkyl ester plasticizer, having between 6 and 13 carbon atoms per alkyl group, of a polybasic acid having between 2 and 4 carboxyl groups, and

between 0.04 and 5 weight percent of the vinyl chloride polymer of a stabilizer consisting essentially of a mixture of between 50 and 90 weight percent of 4,4'- methylene bis-o-cresol and between 10 and 50 weight percent of a polymer of o-cresol and formaldehyde having a molecular weight between about 300 and 1,000.

2. A composition of matter comprising a major portion of a resinous vinyl chloride polymer selected from the group consisting of vinyl chloride homopolymers and vinyl chloride-vinyl acetate copolymers wherein at least 85 weight percent of the copolymer is vinyl chloride, between 20 and weight percent of the polymer of a neutral branched-chain alkyl ester plasticizer, having between 6 and 13 carbon atoms per alkyl group, of a polybasic acid having between 2 and 4 carboxyl groups; between 1 and 12 weight percent of the polymer of at least one stable hydrogen chloride acceptor metal compound selected from the group consisting of compounds of cadmium, barium, zinc, tin and lead; and between 0.04 and 5 weight percent of the vinyl chloride polymer of a stabilizer consisting essentially of a mixture of between 50 and 90 weight percent of 4,4methylene bis-o-cresol and between 10 and 50 weight percent of a polymer of ocresol and formaldehyde having a molecular weight between about 300 and 1,000.

3. A composition of matter comprising a major portion of a resinous copolymer of vinyl chloride and vinyl acetate wherein the weight percent vinyl chloride is at least percent; a neutral branched-chain alkyl ester plasticizer, having between 6 and 13 carbon atoms per alkyl group, of a polybasic acid having between 2 and 4 carboxyl groups; and between 0.04 and 5 weight percent of the vinyl chloride polymer of a stabilizer consisting essentially of a mixture of between 50 and weight percent of 4,4'-methylene bis-o-cresol and between 10 and 50 weight percent of a polymer of o-cresol and formaldehyde having a molecular weight between about 300 and 1,000.

4. A composition according to claim 3 wherein the stabilizer is a mixture of about 70 weight percent 4,4 methylene bis-o-cresol and about 30 weight percent of a polymer of o-cresol and formaldehyde having a molecular weight between about 300 and 1,000.

5. A composition of matter comprising a major portion of a resinous copolymer of vinyl chloride and vinyl acetate wherein the weight percent vinyl chloride is at least 85 percent; between 20 and 80 weight percent of the polymer of a neutral branched-chain alkyl ester plasticizer having between 6 and 13 carbon atoms per alkyl group, of a polybasic acid having between 2 and 4 carboxyl groups; between 1 and 12 weight percent of the polymer of at least one stable hydrogen chloride acceptor metal compound selected from the group consisting of compounds of cadmium, barium, zinc, tin and lead; and between 0.04 and 5 weight percent of the vinyl chloride polymer of a stabilizer consisting essen tially of a mixture of between 50 and 90 weight percent of 4,4-methylene bis-o-cresol and between 10 and 50 weight percent of a polymer of o-cresol and formaldehydeohaving a molecular weight between about 300 and 1,00

6. A composition of matter comprising a major portion of a resinous copolymer of 85 to 97 percent vinyl chloride and 3 to 15 percent vinyl acetate; between 20 and 80 weight percent of the copolymer of a neutral branched-chain alkyl ester plasticizer, having 6 to 13 carbon atoms per alkyl radical, of a polybasic acid having between 2 and 4 carboxyl groups and between 4 and 14 carbon atoms per molecule; between 1 and 12 weight percent of the copolymer of a hydrogen chloride acceptor metal compound stabilizer selected from the group consisting of compounds of cadmium, barium, zinc, tin, and lead; and between 0.04 and 5 weight percent of the vinyl chloride polymer of a stabilizer consisting essentially of a mixture of between 50 and 90 weight percent of 4,4-methylene bis-o-cresol and between 10 and 50 weight percent of a polymer of o-cresol and formaldehyde having a molecular weight between about 300 and 1,000.

7. A composition of matter according to claim 6 wherein the metal compound stabilizer is dibasic lead phthalate. V

8. A composition of matter according to claim 6 wherein the neutral branched-chain ester is ditriclecylphthala-te.

9. A composition of matter according to, claim 7 wherein the auxiliary stabilizer is a mixture of about 70 weight percent"4',4'-methy1ene bis-o-cresol and about 30 8 a weight percent of a polymer of o-cresol and formaldehyde having a molecular weight between about 450 and 850.

9 References Cited by the Examiner UNITED STATES PATENTS 2,421,852 6/1947 Rogers et al. 26043 2,454,209 11/1948 Rogers et al. 260-43 2,829,175 4/1958 Bowman et al. 26045.95 2,862,909 12/1958 Rotelling et a1 26045.95 3,075,940 1/1963 Panzinski et al. 260-4595 MORRIS LIEBMAN, Primary Examiner. 

5. A COMPOSITION OF MATTER COMPRISING A MAJOR PORTION OF A RESINOUS COPOLYMER OF VINYL CHLORIDE AND VINYL ACETATE WHEREIN THE WEIGHT PERCENT VINYL CHLORIDE IS AT LEAST 85 PERCENT; BETWEEN 20 AND 80 WEIGHT PERCENT OF THE POLYMER OF A NEUTRAL BRANCHED-CHAIN ALKYL ESTER PLASTICIZER HAVING BETWEEN 6 AND 13 CARBON ATOMS PER ALKYL GROUP, OF A POLYBASIC ACID HAVING BETWEEN 2 AND 4 CARBOXYL GROUPS; BETWEEN 1 AND 12 WEIGHT PERCENT OF THE POLYMER OF AT LEAST ONE STABLE HYDROGEN CHLORIDE ACCEPTOR METAL COMPOUND SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS OF CADMIUM, BARIUM, ZINC, TIN AND LEAD; AND BETWEEN 0.04 AND 5 WEIGHT PERCENT OF THE VINYL CHLORIDE POLYMER OF A STABILIZER CONSISTING ESSENTIALLY OF A MIXTURE OF BETWEEN 50 AND 90 WEIGHT PERCENT OF 4,4''-METHYLENE NIS-O-CRESOL AND BETWEEN 10 AND 50 WEIGHT PERCENT OF A POLYMER OF O-CRESOL AND FORMALDEHYDE HAVING A MOLECULAR WEIGHT BETWEEN ABOUT 300 AND 1,000. 